@oristarA,
oristarA wrote:
Jack is overjoyed at the good news and forgets keeping his decent manner.
The word
DECENT is not well chosen for this use.
That word is too severe; if Jack is guilty of indecent behavior,
then he might be dragged away in chains, to jail by the police.
A better choice of possible words for the intended meaning is:
self-possessed, or masterful, or suave, or gracious, or urbane,
or facile, or smooth or cultivated, adept, well-bred, deft, glib, or proficient.
There r other reasonable choices.
It might be better rendered:
Jack is overjoyed at the good news and forgets
TO KEEP his self-possessed manner.
David